U.S. patent application number 15/209596 was filed with the patent office on 2016-11-03 for infrared imaging microscope using tunable laser radiation.
The applicant listed for this patent is DAYLIGHT SOLUTIONS, INC.. Invention is credited to Timothy Day, Miles James Weida.
Application Number | 20160320597 15/209596 |
Document ID | / |
Family ID | 47278502 |
Filed Date | 2016-11-03 |
United States Patent
Application |
20160320597 |
Kind Code |
A1 |
Weida; Miles James ; et
al. |
November 3, 2016 |
INFRARED IMAGING MICROSCOPE USING TUNABLE LASER RADIATION
Abstract
An imaging microscope (12) for generating an image of a sample
(10) comprises a beam source (14) that emits a temporally coherent
illumination beam (20), the illumination beam (20) including a
plurality of rays that are directed at the sample (10); an image
sensor (18) that converts an optical image into an array of
electronic signals; and an imaging lens assembly (16) that receives
rays from the beam source (14) that are transmitted through the
sample (10) and forms an image on the image sensor (18). The
imaging lens assembly (16) can further receive rays from the beam
source (14) that are reflected off of the sample (10) and form a
second image on the image sensor (18). The imaging lens assembly
(16) receives the rays from the sample (10) and forms the image on
the image sensor (18) without splitting and recombining the
rays.
Inventors: |
Weida; Miles James; (Poway,
CA) ; Day; Timothy; (Poway, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAYLIGHT SOLUTIONS, INC. |
San Diego |
CA |
US |
|
|
Family ID: |
47278502 |
Appl. No.: |
15/209596 |
Filed: |
July 13, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14353487 |
Apr 22, 2014 |
9432592 |
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PCT/US12/61987 |
Oct 25, 2012 |
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15209596 |
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61551147 |
Oct 25, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 21/0088 20130101;
G02B 21/088 20130101; G02B 21/365 20130101; H04N 5/33 20130101;
G02B 21/0056 20130101; G02B 21/00 20130101 |
International
Class: |
G02B 21/00 20060101
G02B021/00; H04N 5/33 20060101 H04N005/33; G02B 21/36 20060101
G02B021/36 |
Goverment Interests
GOVERNMENT SPONSORED DEVELOPMENT
[0004] The U.S. Government has rights in this invention pursuant to
contract number NSF SBIR Phase I Award No. II-1046450 with the
National Science Foundation.
Claims
1-20. (canceled)
21. An imaging microscope for generating a two-dimensional image of
a sample, the imaging microscope comprising: a beam source that
emits a temporally coherent illumination beam, the illumination
beam including a plurality of rays; an illumination lens assembly
that directs the illumination beam at the sample, the illumination
lens assembly adjusting the illumination beam so that the
illumination beam illuminates a two-dimensional illuminated area on
the sample all at once; an image sensor that converts an optical
image into an array of electronic signals, the image sensor
including a two-dimensional array of sensors that are used to
construct a two-dimensional image; and an imaging lens assembly
that receives rays from the beam source that are transmitted
through the sample and forms a two-dimensional, first image on the
image sensor.
22. The imaging microscope of claim 21 wherein the illumination
lens assembly directs the illumination beam at the sample without
splitting and recombining the illumination beam
23. The imaging microscope of claim 21 wherein the imaging lens
assembly receives the rays from a plurality of points on the sample
and forms the first image on the image sensor without splitting and
recombining the received rays.
24. The imaging microscope of claim 21 wherein the beam source is a
MIR beam source and the illumination beam is at a beam wavelength
that is within the MIR range; and wherein the illumination lens
assembly is refractive in the MIR range.
25. The imaging microscope of claim 21 wherein the illumination
lens assembly magnifies the illumination beam.
26. The imaging microscope of claim 25 wherein the illumination
lens assembly adjusts the size of the illumination beam so that the
illuminated area on the sample is at least approximately twenty
millimeters squared.
27. The imaging microscope of claim 21 wherein the imaging lens
assembly collimates the received rays.
28. The imaging microscope of claim 21 wherein the beam source
further emits a temporally coherent, second illumination beam, the
second illumination beam including a plurality of second rays;
wherein the imaging microscope includes a reflection lens assembly
that directs the second illumination beam at the sample without
splitting and recombining the second illumination beam, the
reflection lens assembly adjusting the second illumination beam so
that the second illumination beam illuminates a two-dimensional
illuminated area on the sample all at once; and wherein the imaging
lens assembly further receives second rays from the second
illumination beam that are reflected off of the sample and forms a
two-dimensional, second image on the image sensor without splitting
and recombining the received second rays.
29. An imaging microscope for generating a two-dimensional image of
a sample, the imaging microscope comprising: a beam source that
emits a temporally coherent illumination beam, the illumination
beam including a plurality of rays; a reflection lens assembly that
directs the illumination beam at the sample, the reflection lens
assembly adjusting the illumination beam so that the illumination
beam illuminates a two-dimensional illuminated area on the sample
all at once; an image sensor that converts an optical image into an
array of electronic signals, the image sensor including a
two-dimensional array of sensors that are used to construct the
two-dimensional image; and an imaging lens assembly that receives
rays from the beam source that are reflected off of the sample and
forms a two-dimensional image on the image sensor.
30. The imaging microscope of claim 29 wherein the reflection lens
assembly directs the illumination beam at the sample without
splitting and recombining the illumination beam.
31. The imaging microscope of claim 29 wherein the imaging lens
assembly receives the rays from a plurality of points on the sample
and forms the image on the image sensor without splitting and
recombining the received rays.
32. The imaging microscope of claim 29 wherein the imaging lens
assembly includes an objective lens and a projection lens, and
wherein the imaging microscope further includes a beam splitter
positioned between the objective lens and the projection lens, the
beam splitter redirecting a first portion of the rays received by
the imaging lens assembly at the sample, and the beam splitter
transmitting a second portion of the rays received by the imaging
lens assembly.
33. The imaging microscope of claim 29 wherein the beam source is a
MIR beam source and the illumination beam is at a beam wavelength
that is within the MIR range; and wherein the reflection lens
assembly is refractive in the MIR range.
34. The imaging microscope of claim 29 wherein the reflection lens
assembly magnifies the illumination beam.
35. The imaging microscope of claim 29 wherein the reflection lens
assembly adjusts the size of the illumination beam so that the
illuminated area on the sample is at least approximately twenty
millimeters squared.
36. The imaging microscope of claim 29 wherein the imaging lens
assembly collimates the received rays.
37. A method for generating a two-dimensional image of a sample,
the method comprising: emitting a temporally coherent illumination
beam with a beam source, the illumination beam including a
plurality of rays; directing the illumination beam at the sample
with an illumination lens assembly, the illumination lens assembly
adjusting the illumination beam so that the illumination beam
illuminates a two-dimensional illuminated area on the sample all at
once; converting an optical image into an array of electronic
signals with an image sensor, the image sensor including the
two-dimensional array of sensors that are used to construct a
two-dimensional image; receiving rays from the beam source that are
transmitted through the sample with an imaging lens assembly; and
forming a two-dimensional, first image on the image sensor with the
rays received from the beam source by the imaging lens assembly
that are transmitted through the sample.
38. The method of claim 37 further comprising (i) emitting a
temporally coherent, second illumination beam with the beam source,
the second illumination beam including a plurality of second rays;
(ii) directing the second illumination beam at the sample with a
reflection lens assembly, the reflection lens assembly adjusting
the second illumination beam so that the second illumination beam
illuminates a two-dimensional illuminated area on the sample all at
once; (iii) receiving second rays from the beam source that are
reflected off of the sample with the imaging lens assembly; and
(iv) forming a two-dimensional second image on the image sensor
with the second rays received from the beam source by the imaging
lens assembly that are reflected off of the sample.
39. A method for generating a two-dimensional image of a sample,
the method comprising the steps of: emitting a temporally coherent
illumination beam with a beam source, the illumination beam
including a plurality of rays; directing the illumination beam at
the sample with a reflection lens assembly that adjusts the
illumination beam so that the illumination beam illuminates a
two-dimensional illuminated area on the sample all at once;
converting an optical image into an array of electronic signals
with an image sensor, the image sensor including a two-dimensional
array of sensors that are used to construct the two-dimensional
image; receiving rays from the beam source that are reflected off
of the sample with an imaging lens assembly; and forming a
two-dimensional image on the image sensor with the rays received
from the beam source by the imaging lens assembly that are
reflected off of the sample.
Description
RELATED INVENTION
[0001] This application is a continuation application of U.S.
application Ser. No. 14/353,487, filed Apr. 22, 2014 and entitled
"INFRARED IMAGING MICROSCOPE USING TUNABLE LASER RADIATION". As far
as permitted, the contents of U.S. application Ser. No. 14/353,487
are incorporated herein by reference.
[0002] U.S. application Ser. No. 14/353,487 is a 371 of
PCT/US12/61987, filed Oct. 25, 2012 and entitled "INFRARED IMAGING
MICROSCOPE USING TUNABLE LASER RADIATION". As far as permitted, the
contents of PCT/US12/61987 are incorporated herein by
reference.
[0003] PCT/US12/61987 claims priority on U.S. Provisional
Application Ser. No. 61/551,147, filed Oct. 25, 2011 and entitled
"INFRARED IMAGING MICROSCOPE USING TUNABLE LASER RADIATION FOR
SPECTROSCOPIC ANALYSIS OF SAMPLES". As far as permitted, the
contents of U.S. Provisional Application Ser. No. 61/551,147 are
incorporated herein by reference.
BACKGROUND
[0005] Microscopes are often used to analyze a sample in order to
evaluate certain details and/or properties of the sample that would
not otherwise be visible to the naked eye. Additional information
on the chemical properties of the sample can be obtained by
illuminating and observing the sample with distinct wavelengths of
monochromatic laser radiation. Samples that can be analyzed this
way include human tissue, explosive residues, powders, liquids,
solids, inks, and other materials. A human tissue sample may be
analyzed for the presence of cancerous cells and/or other health
related conditions. Other materials may be analyzed for the
presence of explosive residues and/or other dangerous
substances.
SUMMARY
[0006] The present invention is directed toward an imaging
microscope for generating an image of a sample, the imaging
microscope comprising a beam source, an image sensor and an imaging
lens assembly. The beam source emits a temporally coherent
illumination beam, the illumination beam including a plurality of
rays that are directed at the sample. The image sensor converts an
optical image into an array of electronic signals. In one
embodiment, the imaging lens assembly receives rays from the beam
source that are transmitted through the sample and form an image on
the image sensor. Alternatively, the imaging lens assembly can
receive rays from the beam source that are reflected off of the
sample to form the image on the image sensor.
[0007] In certain embodiments, the imaging microscope further
comprises an illumination lens assembly that directs the
illumination beam at the sample. The illumination lens assembly
adjusts the illumination beam so that the illumination beam
illuminates a two-dimensional illuminated area on the sample all at
once. Additionally, in such embodiments, the image sensor includes
a two-dimensional array of sensors.
[0008] In one embodiment, the beam source is a mid-infrared ("MIR")
beam source and the illumination beam is at a beam wavelength that
is within the MIR range. In this embodiment, the illumination lens
assembly is refractive in the MIR range.
[0009] Additionally, in some embodiments, the illumination lens
assembly directs the illumination beam at the sample without
splitting and recombining the illumination beam.
[0010] Further, in one embodiment, the illumination lens assembly
magnifies the illumination beam. Moreover, the illumination lens
assembly can adjust the size of the illumination beam so that the
illuminated area on the sample is at least approximately two
hundred and fifty microns by two hundred and fifty microns.
[0011] In one embodiment, the imaging lens assembly includes a
refractive lens that directs the rays received by the imaging lens
assembly.
[0012] Additionally, in some embodiments, the imaging lens assembly
receives the rays from a plurality of points on the sample and
forms the image on the image sensor without splitting and
recombining the received rays.
[0013] The present invention is further directed toward a method
for generating an image of a sample, the method comprising the
steps of emitting a temporally coherent illumination beam with a
beam source, the illumination beam including a plurality of rays;
directing the plurality of rays at the sample; converting an
optical image into an array of electronic signals with an image
sensor; receiving rays from the beam source that are transmitted
through the sample with an imaging lens assembly; and forming an
image on the image sensor with the rays received from the beam
source by the imaging lens assembly that are transmitted through
the sample.
[0014] Additionally and/or alternatively, the method can further
comprise the steps of receiving rays from the beam source that are
reflected off of the sample with the imaging lens assembly; and
forming a second image on the image sensor with the rays received
from the beam source by the imaging lens assembly that are
reflected off of the sample.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The novel features of this invention, as well as the
invention itself, both as to its structure and its operation, will
be best understood from the accompanying drawings, taken in
conjunction with the accompanying description, in which similar
reference characters refer to similar parts, and in which:
[0016] FIG. 1A is simplified schematic illustration of a sample and
an embodiment of an imaging microscope having features of the
present invention;
[0017] FIG. 1B is a simplified schematic illustration of the sample
illustrated in FIG. 1A, including a transmission illuminated
area;
[0018] FIG. 1C is a simplified schematic illustration of the sample
illustrated in FIG. 1A, including a reflection illuminated
area;
[0019] FIG. 2 is a simplified schematic illustration of the sample
and another embodiment of an imaging microscope having features of
the present invention;
[0020] FIG. 3 is a simplified schematic illustration of the sample
and still another embodiment of an imaging microscope having
features of the present invention; and
[0021] FIG. 4 is a simplified flowchart demonstrating the use of an
imaging microscope having features of the present invention to
analyze a sample.
DESCRIPTION
[0022] FIG. 1A is simplified schematic illustration of a sample 10
and a first embodiment of an imaging microscope 12 having features
of the present invention. In particular, the imaging microscope 12
can be used to analyze and evaluate the various properties of the
sample 10. For example, in one embodiment, the imaging microscope
12 is an infrared imaging microscope that uses tunable laser
radiation to spectroscopically interrogate one or more samples 10
in order to analyze and identify the properties of the sample.
[0023] As an overview, the imaging microscope 12 is uniquely
designed to inhibit potential complications from temporal and/or
spatial coherence that may otherwise be present due to the use of
laser radiation for image illumination. Moreover, the present
invention provides such benefits without the potential drawbacks of
complexity of manufacture and operation, increased size and time
requirements, increased power consumption, high cost, and
inefficiency.
[0024] The sample 10 can be a variety of things, including human
tissue, animal tissue, plant matter, explosive residues, powders,
liquids, solids, inks, and other materials commonly analyzed using
Fourier transform infrared (FTIR) microscopes. More particularly,
in certain non-exclusive applications, the sample 10 can be human
tissue and the imaging microscope 12 can be utilized for rapid
screening of the tissue sample 10 for the presence of cancerous
cells and/or other health related conditions; and/or the imaging
microscope 12 can be utilized in certain forensic applications such
as rapid screening of the sample 10 for the presence of explosive
residues and/or other dangerous substances. Additionally, when
positioned substantially within the imaging microscope 12 for
purposes of analysis, the sample 10 can be present by itself, or
the sample 10 can be held in place using one or more slides, e.g.,
infrared transparent slides.
[0025] Further, the sample 10 can be thin enough to allow study
through transmission of an illumination beam, e.g., an infrared
illumination beam, through the sample 10 (i.e. in transmission
mode), or the sample 10 can be an optically opaque sample that is
analyzed through reflection of an illumination beam, e.g., an
infrared illumination beam, by the sample (i.e. in reflection
mode). For example, in the embodiment illustrated in FIG. 1A, the
imaging microscope 12 can alternatively be utilized in both
transmission mode and reflection mode.
[0026] In another embodiment, the imaging mircroscope 12 can be
used in both transmission mode and reflection mode at the same
time. For example, some samples 10 are transmissive to certain
wavelengths and reflective to other wavelengths. As a more
specific, non-exclusive example, light in the visible spectrum can
be directed at the sample 10 for use in the transmission mode, and
MIR light can be directed at the sample 10 for use in the
reflection mode. Still alternatively, the imaging microscope 12 can
be designed such that it only operates in one of transmission mode
or reflection mode.
[0027] The design of the imaging microscope 12 can be varied. In
the embodiment illustrated in FIG. 1A, the imaging microscope 12
includes a rigid frame 13, a temporally coherent beam source 14, a
stage assembly 15 that retains the sample 10, an imaging lens
assembly 16 (e.g., one or more lenses), and an image sensor 18 that
converts an optical image into an array of electronic signals. The
design of each of these components can be varied pursuant to the
teachings provided herein.
[0028] In one embodiment, the beam source 14 (i) emits a temporally
coherent, first illumination beam 20 that is usable for
illuminating and analyzing the sample 10 in transmission mode;
and/or (ii) emits a temporally coherent, second illumination beam
22 that is usable for illuminating and analyzing the sample 10 in
reflection mode. The first illumination beam 20 is made up of a
plurality of illumination rays 20l that are directed at the sample
10, and the second illumination beam 22 is made up of a plurality
of illumination rays 22l that are directed at the sample 10. Each
illumination beam 20, 22 can be emitted from the same beam source
14. Alternatively, each illumination beam 20, 22 can be emitted
from a separate and distinct beam source. It should be noted that
the use of the terms "first illumination beam" and "second
illumination beam" is merely for ease of description, and either
illumination beam 20, 22 can be referred to as the "first
illumination beam" or the "second illumination beam".
[0029] In certain embodiments, the beam source 14 can include (i) a
first laser source 14A that emits the first illumination beam 20,
e.g., a first laser beam, and (ii) a second laser source 14B that
emits the second illumination beam 22, e.g., a second laser beam.
Alternatively, for example, the beam source 14 can be designed to
include a single laser source with the appropriate beam
directors.
[0030] Further, in one, non-exclusive embodiment, the beam source
14 is designed to provide illumination beams 20, 22 that are in the
mid infrared ("MIR") range spectrum. More particularly, in some
such embodiments, one or both of the laser sources 14A, 14B can be
a mid-infrared (MIR) beam source that emits the first illumination
beam 20 and/or the second illumination beam 22 that is at a beam
wavelength that is within the MIR range. For example, one or both
of the laser sources 14A, 14B can be any type of laser that is
capable of generating radiation in the spectral region of between
approximately two to twenty microns (2-20 .mu.m). Moreover, in
alternative embodiments, the laser sources 14A, 14B can be a pulsed
laser and/or a continuous wave (CW) laser.
[0031] As provided herein, one or both of the laser sources 14A,
14B can be an external cavity laser that includes a laser frame
14C, a gain medium 14D, a cavity optical assembly 14E, an output
optical assembly 14F, and a wavelength dependent ("WD") feedback
assembly 14G.
[0032] The laser frame 14C provides a rigid support for the
components of each laser source 14A, 14B. In one embodiment, the
laser frame 14C for each laser source 14A, 14B is a single
mechanical ground plane that provides structural integrity for the
respective laser source 14A, 14B. In certain embodiments, the laser
frame 14C is made of rigid material that has a relatively high
thermal conductivity.
[0033] The design of the gain medium 14D can be varied pursuant to
the teachings provided herein. In one, non-exclusive embodiment,
the gain medium 14D for each laser directly emits the respective
beams 20, 22 without any frequency conversion. As non-exclusive
examples, one or both of the gain mediums 14D can be a Quantum
Cascade (QC) gain medium, an Interband Cascade (IC) gain medium, or
a mid-infrared diode. Alternatively, another type of gain medium
14D can be utilized.
[0034] In FIG. 1A, each gain medium 14D includes (i) a first facet
that faces the respective cavity optical assembly 14E and the
feedback assembly 14G, and (ii) a second facet that faces the
output optical assembly 14F. In this embodiment, each gain medium
14D emits from both facets. In one embodiment, each first facet is
coated with an anti-reflection ("AR") coating, and each second
facet is coated with a reflective coating. The AR coating allows
light directed from the gain medium 14D at the first facet to
easily exit as a beam directed at the feedback assembly 14G; and
allows the light beam reflected from the feedback assembly 14G to
easily enter the gain medium 14D. The beams 20, 22 exit from the
respective second facet. The partly reflective coating on the
second facet of each gain medium 14D reflects at least some of the
light that is directed at the second facet of each gain medium 14D
back into the respective gain medium 14D. In one non-exclusive
embodiment, the AR coating can have a reflectivity of less than
approximately 2 percent, and the reflective coating can have a
reflectivity of between approximately 2-95 percent.
[0035] In one embodiment, for each laser source 14A, 14B, (i) the
reflective coating on the second facet of the gain medium 14D acts
as a first end (output coupler) of an external cavity and the
feedback assembly 14G (spaced apart from the gain medium 14D)
defines a second end of the each external cavity. The term external
cavity is utilized to designate that the WD feedback assembly 14G
is positioned outside of the gain medium 14D.
[0036] The cavity optical assembly 14E is positioned between the
gain medium 14D and the feedback assembly 14G along a lasing axis.
The cavity optical assembly 14E collimates and focuses the beam
that passes between these components. For example, each cavity
optical assembly 14E can include one or more lens. For example, the
lens can be an aspherical lens having an optical axis that is
aligned with the respective lasing axis.
[0037] The output optical assembly 14F is positioned between the
gain medium 14D and the beam redirector assembly 28 in line with
the lasing axis to collimate and focus the beam 22 that exits the
second facet of the gain medium 14D. For example, each output
optical assembly 14F can include one or more lens that are somewhat
similar in design to the lens of the cavity optical assemblies
14E.
[0038] The WD feedback assembly 14G reflects the beam back to the
gain medium 14D, and is used to precisely select and adjust the
lasing frequency of the external cavity and the wavelength of the
pulses of light. Stated in another fashion, the WD feedback
assembly 14G is used to feed back to the gain medium 14D a
relatively narrow band wavelength which is then amplified in the
respective gain medium 14D. In this manner, the respective beams
20, 22 may be tuned with the WD feedback assembly 14G without
adjusting the respective gain medium 14D. Thus, with the external
cavity arrangements disclosed herein, the WD feedback assembly 14G
dictates what wavelength will experience the most gain and thus
dominate the wavelength of the beams 20, 22.
[0039] In one embodiment, the WD feedback assembly 14G includes a
diffraction grating 14H and a grating mover 141 that selectively
moves (e.g. rotates) the grating 14H to adjust the lasing frequency
of the gain medium 14D and the wavelength of the respective beams
20, 22. The grating 14H can be continuously monitored with an
encoder that provides for closed loop control of the grating mover
141. With this design, the wavelength of the respective beam 20, 22
can be selectively adjusted in a closed loop fashion so that the
sample 10 can be imaged at many different, precise, selectively
adjustable wavelengths throughout a portion or the entire MIR
spectrum.
[0040] Once the beam source 14 has emitted the first illumination
beam 20 and/or the second illumination beam 22, the illumination
beam 20, 22 is directed toward the sample 10 so that the sample 10
may be properly and effectively illuminated by the illumination
beam 20, 22. For example, when the imaging microscope 12 is
operating in transmission mode, the first illumination beam 20
(including the plurality of illumination rays 20l) is directed
toward the sample 10 in order to properly and effectively
illuminate the sample 10. In this example, the rays that are
transmitted through the sample 10 are referred to as transmitted
rays 20T. In another example, when the imaging microscope 12 is
operating in reflection mode, the second illumination beam 22
(including a plurality of illumination rays 22l) is directed toward
the sample 10 in order to properly and effectively illuminate the
sample 10. In this example, the rays that are reflected off of the
sample 10 are referred to as reflected rays 22R.
[0041] In the embodiment illustrated in FIG. 1A, when operating in
transmission mode, the first illumination beam 20 exiting the beam
source 14 is directed with a transmission illumination lens
assembly 24 toward and impinging on the sample 10. In one
embodiment, the transmission illumination lens assembly 24 can
include one or more refractive lenses 24A (only one is illustrated
in phantom) that direct the first illumination beam 20 at the
sample 10. Moreover, the transmission illumination lens assembly 24
can be refractive in the MIR range.
[0042] In certain embodiments, the transmission illumination lens
assembly 24 adjusts the first illumination beam 20 so that the
first illumination beam 20 at least illuminates a transmission
illuminated area 10A (illustrated in FIG. 1B) on the sample 10 all
at once that is two-dimensional 10. Stated in another fashion, the
transmission illumination lens assembly 24 adjusts the first
illumination beam 20 so that the first illumination beam 20 at
least illuminates a two-dimensional transmission illuminated area
10A simultaneously on the sample 10. With this design, the entire
sample 10 or a large portion of the sample 10 is simultaneously
illuminated and can be examined at the same time. This expedites
the analysis of the sample 10.
[0043] In certain embodiments, the transmission illumination lens
assembly 24 can be used to transform, i.e. to increase (magnify) or
decrease, the size of the first illumination beam 20 to match and
simultaneously illuminate a desired transmission illuminated area
10A on the sample 10. Stated another way, the transmission
illumination lens assembly 24 can be used to condition and focus
the first illumination beam 20 so that the first illumination beam
20 has the correct or desired size and beam profile on the sample
10. In certain embodiments, size of the transmission illuminated
area 10A of the sample 10 is tailored to correspond to the design
of the image sensor 18 and the imaging lens assembly 16.
[0044] FIG. 1B is a simplified schematic illustration of the sample
10 illustrated in FIG. 1A, including the transmission illuminated
area 10A (illustrated with a box in phantom) that is simultaneously
illuminated. In certain embodiments, the two-dimensional
transmission illumination area 10A is rectangular shaped. More
particularly, in some such embodiments, the two-dimensional
transmission illumination area 10A can be square shaped. For
example, in alternative non-exclusive embodiments, the transmission
illumination lens assembly 24 can adjust the size of the first
illumination beam 20 so that the transmission illuminated area 10A
that is simultaneously illuminated on the sample 10 is at least
approximately (i) two hundred and fifty microns (250 .mu.m) by two
hundred and fifty microns (250 .mu.m); (ii) five hundred microns
(500 .mu.m) by five hundred microns (500 .mu.m); (iii) seven
hundred and fifty microns (750 .mu.m) by seven hundred and fifty
microns (750 .mu.m); (iv) one millimeter (1 mm) by one millimeter
(1 mm); (v) one and a half millimeter (1.5 mm) by one and a half
millimeter (1.5 mm); and (vi) two millimeters (2 mm) by two
millimeters (2 mm); or (vii) three millimeters (3 mm) by three
millimeters (3 mm). Still alternatively, the transmission
illuminated area 10A can have a non-square shape. As non-exclusive
examples, the transmission illumination lens assembly 24 can adjust
the size of the first illumination beam 20 so that the transmission
illuminated area 10A on the sample 10 is at least approximately two
hundred microns (200 .mu.m) by three hundred microns (300 .mu.m);
or (iii) fifty microns (50 .mu.m) by five hundred microns (500
.mu.m). Alternatively, the transmission illumination lens assembly
24 can adjust the size of the first illumination beam 20 so that
the transmission illuminated area 10A on the sample 10 has a
different size or shape than the examples provided above. For
example, in alternative, non-exclusive embodiments, the
transmission illumination lens assembly 24 can adjust the size of
the first illumination beam 20 so that the transmission illuminated
area 10A is at least approximately 20, 30, 30, 50, 60, 70, 80, 90,
or 100 millimeters squared. Still alternatively, for example, the
two-dimensional transmission illuminated area 10A can be circular
or oval shaped.
[0045] Further, as shown in FIG. 1B, the transmission illuminated
area 10A is really an effectively illuminated area (has
substantially uniform intensity) that exists within a larger, fully
illuminated area 10B that is simultaneously illuminated by the
first illumination beam 20 (illustrated in FIG. 1A). As
illustrated, the fully illuminated area 10B can be substantially
circular shaped and can be the result of the first illumination
beam 20 having a substantially circular shaped cross-section.
Alternatively, the first illumination beam 20, and thus the fully
illuminated area 10B can have another shape.
[0046] Moreover, referring back to FIG. 1A, the transmission
illumination lens assembly 24 transforms the size and profile of
the first illumination beam 20 as desired without splitting the
illumination rays 20l of the first illumination beam 20 into
multiple paths that, if recombined, can cause interference at the
sample 10. Stated another way, the transmission illumination lens
assembly 24 directs the first illumination beam 20 at the sample 10
without splitting and recombining the illumination rays 20l of the
first illumination beam 20.
[0047] Alternatively, in another embodiment, if the first
illumination beam 20 has sufficient extent to allow illumination of
the desired area size of the sample 10, then the imaging microscope
12 can be designed without the transmission illumination lens
assembly 24, and the first illumination beam 20 can be directly
shined onto the sample 10.
[0048] In the embodiment illustrated in FIG. 1A, the imaging
microscope 12 also can include a reflection illumination lens
assembly 26 for directing the second illumination beam 22 at the
sample 10 when operating in reflection mode. In one embodiment, the
reflection illumination lens assembly 26 includes one or more
lenses 26A, a redirector 28, e.g., a mirror, and a
transmitter-redirector 30, e.g., a beam splitter. In this
embodiment, one or more of the lenses 26A of the reflection
illumination lens assembly 26 can be refractive in the MIR range.
In the non-exclusive embodiment illustrated in FIG. 1A, the lens
assembly 26 includes two, spaced apart lenses 26A.
[0049] Additionally, in certain embodiments, the reflection
illumination lens assembly 26 adjusts the second illumination beam
22 so that the second illumination beam 22 at least illuminates a
reflection illuminated area 10C (illustrated in FIG. 1C) on the
sample 10 all at once that is two-dimensional. Stated in another
fashion, the reflection illumination lens assembly 26 adjusts the
second illumination beam 22 so that the second illumination beam 22
illuminates a two-dimensional reflection illuminated area 10C
simultaneously on the sample 10. With this design, the entire
sample 10 or a large portion of the sample 10 is simultaneously
illuminated and can be examined at the same time. This expedites
the analysis of the sample 10. In certain embodiments, the
reflection illumination lens assembly 26 conditions the second
illumination beam 22 to allow for the broad illumination of the
reflection illuminated area 10C through a first lens 32 of the
imaging lens assembly 16. In this embodiment, the same first lens
32 is used direct the second illumination beam 22 at the sample 10
and is used as the objective for the beams reflected off the sample
10.
[0050] In certain embodiments, the reflection illumination lens
assembly 26 can be used to transform, i.e. to increase (magnify) or
decrease, the size of the second illumination beam 22 to match a
desired reflection illuminated area 10C on the sample 10. Stated
another way, the reflection illumination lens assembly 26 can be
used to condition and focus the second illumination beam 22 so that
the second illumination beam 22 has the desired beam profile on the
sample 10.
[0051] FIG. 1C is a simplified schematic illustration of the sample
10 including the reflection illuminated area 10C. In certain
embodiments, the two-dimensional reflection illumination area 10C
is rectangular shaped. More particularly, in some such embodiments,
the two-dimensional reflection illumination area 10C can be square
shaped. For example, in alternative, non-exclusive embodiments, the
reflection illumination lens assembly 26 can adjust the size of the
second illumination beam 22 so that the reflection illuminated area
10C on the sample 10 is at least approximately (i) two hundred and
fifty microns (250 .mu.m) by two hundred and fifty microns (250
.mu.m); (ii) five hundred microns (500 .mu.m) by five hundred
microns (500 .mu.m); (iii) seven hundred and fifty microns (750
.mu.m) by seven hundred and fifty microns (750 .mu.m); (iv) one
millimeter (1 mm) by one millimeter (1 mm); (v) one and a half
millimeter (1.5 mm) by one and a half millimeter (1.5 mm); and (vi)
two millimeters (2 mm) by two millimeters (2 mm); or (vii) three
millimeters (3 mm) by three millimeters (3 mm). Still
alternatively, the reflection illuminated area 10C can have a
non-square shape. As non-exclusive examples, the transmission
illumination lens assembly 24 can adjust the size of the first
illumination beam 20 so that the transmission illuminated area 10A
on the sample 10 is at least approximately two hundred microns (200
.mu.m) by three hundred microns (300 .mu.m); or (iii) fifty microns
(50 .mu.m) by five hundred microns (500 .mu.m). Alternatively, the
reflection illumination lens assembly 26 can adjust the size of the
second illumination beam 22 so that the reflection illuminated area
10C on the sample 10 has a different size or shape than the
examples provided above. For example, in alternative, non-exclusive
embodiments, the reflection illumination lens assembly 26 can
adjust the size of the second illumination beam 22 so that the
reflection illuminated area 10C is at least approximately 20, 30,
30, 50, 60, 70, 80, 90, or 100 millimeters squared. Still
alternatively, for example, the two-dimensional reflection
illuminated area 10C can be circular or oval shaped.
[0052] Further, as shown in FIG. 1C, the reflection illuminated
area 10C can be an effectively illuminated area (has substantially
uniform intensity) that exists within a larger, fully illuminated
area 10D that is illuminated by the second illumination beam 22
(illustrated in FIG. 1A). As illustrated, the fully illuminated
area 10D can be substantially circular shaped and can be the result
of the second illumination beam 22 having a substantially circular
shaped cross-section. Alternatively, the second illumination beam
22, and thus the fully illuminated area 10C can have another
shape.
[0053] Referring back to FIG. 1A, in certain embodiments, the
reflection illumination lens assembly 26 transforms the size and
profile of the second illumination beam 22 as desired without
splitting and recombining the illumination rays 22l into multiple
paths that, if recombined, can cause interference at the sample 10.
Stated another way, the reflection illumination lens assembly 26
directs the illumination rays 22l of the second illumination beam
22 at the sample 10 without splitting and recombining the
illumination rays 22l.
[0054] Additionally, in alternative embodiments, the reflection
illumination lens assembly 26 can be positioned such that the
second illumination beam 22 passes through the reflection
illumination lens assembly 26 before and/or after the second
illumination beam 22 is redirected by the redirector 28.
[0055] The redirector 28 is utilized to initially redirect the
second illumination beam 22 so that the second illumination beam 22
can be properly directed toward a side (e.g. the bottom or the top
depending on the design) of the sample 10 that will reflect the
second illumination beam 22 toward the imaging lens assembly 16.
The design of the redirector 28 can be varied. In one embodiment,
the redirector 28 can be a mirror (reflective in the desired
wavelength spectrum) which is positioned so as to redirect the path
of the second illumination beam 22 by approximately ninety degrees.
Alternatively, the redirector 28 can have a different design and/or
the redirector 28 can be positioned so as to redirect the path of
the second illumination beam 22 by greater than or less than
approximately ninety degrees. Still alternatively, the redirector
28 can include a curved mirror that conditions the second
illumination beam 22 (i) to complement the reflection illumination
lens assembly 26, or (ii) to allow for the elimination of a portion
or all of the reflection illumination lens assembly 26.
[0056] Moreover, in reflection mode, in FIG. 1A, the second
illumination beam 22 is directed at the sample 10 with the
transmitter-redirector 30 to avoid multiple beam paths, and to
decrease the number of paths the reflected or scattered second
illumination beam 22 can take when traveling from the sample 10 to
the image sensor 18. The design of the transmitter-redirector 30
can be varied to suit the specific requirements of the imaging
microscope 12. In certain embodiments, the transmitter-redirector
30 can be a beam splitter, e.g., a fifty percent (50%) beam
splitter, which redirects a first portion 22F of the illumination
rays 22l of the second illumination beam 22 toward the sample 10,
and transmits a second portion (not shown) of the illumination rays
22l of the second illumination beam 22. The second portion of the
second illumination beam 22 is subsequently directed away from the
system and not used by the imaging microscope 12. It should be
noted that the second (or discarded) portion of the second
illumination beam 22 that is generated from this first pass through
the transmitter-redirector 30 is not shown in FIG. 1A for purposes
of clarity.
[0057] With the second illumination beam 22 being redirected by the
transmitter-redirector 30 before impinging on the sample 10, as
provided above, the reflection illumination lens assembly 26 can be
used to transform the second illumination beam 22 so that it
provides illumination for the two-dimensional reflection
illuminated area 10C across the sample 10, instead of being focused
to a point by the first lens 32 of the imaging lens assembly 16. In
certain embodiments, the transmitter-redirector 30 can be made from
a variety of infrared transmissive materials, such as ZnSe or Ge,
or other materials. Additionally, the transmitter-redirector 30 can
be a plano-piano beam splitter, with one side anti-reflection (AR)
coated, and the other coated or uncoated for partial reflectivity.
The transmitter-redirector 30 can also provide lensing action for
transforming the second illumination beam 22 as desired. The
transmitter-redirector 30 can also incorporate design elements to
eliminate first and second surface interference effects due to the
coherent nature of the illumination beam 22. As non-exclusive
examples, design elements that would reduce the surface
interference effects include anti-reflective coatings (for the
wavelength of the beam), wedged elements, and/or curved optical
surfaces.
[0058] The stage assembly 15 retains the sample 10, and can be used
to properly position the sample 10. For example, the stage assembly
15 can include a stage 15A that retains sample 10, and stage mover
15B that selectively moves the stage 15A and the sample 10. For
example, the stage mover 15B can include one or more actuators, or
stage 15A can be manually positioned.
[0059] When the illumination rays 20l of the first illumination
beam 20 are illuminating the sample 10, at least a portion of the
transmitted rays 20T that are transmitted through the sample 10 are
received by the imaging lens assembly 16 and imaged on the image
sensor 18. Somewhat similarly, when the illumination rays 22l of
the second illumination beam 22 are illuminating the sample 10, at
least a portion of the reflected rays 22R that are reflected from
the sample 10 are received by the imaging lens assembly 16 and
imaged on the image sensor 18. Stated in another fashion, the
imaging lens assembly 16 receives at least a portion of the
transmitted rays 20T that are transmitted through the sample 10, or
at least a portion of the reflected rays 22R that are reflected
from the sample 10 and forms an image on the image sensor 18.
[0060] As utilized herein, the term "imaged rays" 18A shall mean
the transmitted rays 20T or the reflected rays 22R that are
collected by the imaging lens assembly 16 and imaged on the image
sensor 18. As provided herein, the imaging lens assembly 16
receives the imaged rays 18A from a plurality of points on the
sample 10 and forms the image on the image sensor 18 without
splitting and recombining the imaged rays 18A. This reduces
interference effects at the image sensor 18.
[0061] In one embodiment, the imaging lens assembly 16 can include
a first lens 32 and a second lens 34 that cooperate to form an
image of the sample 10 on the image sensor 18. Alternatively, the
imaging lens assembly 16 can include greater than two lenses or
only one lens.
[0062] In one embodiment, the first lens 32 can be an objective
lens that collects the imaged rays 18A, and focuses the imaged rays
18A on the image sensor 18. Moreover, as illustrated, the first
lens 32 is positioned substantially between the sample 10 and the
second lens 34. Additionally, in one embodiment, the second lens 34
can be a projection lens that projects the imaged rays 18A toward
the image sensor 18. Moreover, as illustrated, the second lens 34
is positioned substantially between the first lens 32 and the image
sensor 18. Further, in one embodiment, one or both of the lenses
32, 34 can be refractive in the MIR range or the wavelength of the
illumination beam. Still further, one or both of the lenses 32, 34
can be a compound lens.
[0063] Each of the lenses 32, 34 can be types such as plano-convex,
plano-concave, miniscus, and aspherical, as well as other types.
For refractive lenses, materials such as ZnSe, Ge, chalcogenide
glass, and other materials can be employed. Reflective lenses can
be elliptical, paraboloid, or other shapes. The reflective surface
can be dichroic coating, Au, Ag, or other surface types. In one
non-exclusive embodiment, the first lens 32, i.e. the objective
lens, can be a 10 millimeter diameter, 10 millimeter focal length,
plano-aspheric Ge lens, and the second lens 34, i.e. the projection
lens, can be a 20 millimeter diameter, 50 millimeter focal length
plano-convex Ge lens. This provides a magnification of 5.times. at
the image sensor 18, allowing an image resolution of 3.4 .mu.m for
a 17 .mu.m pitch pixel. It should be noted that the resolution of
the image sensor 18 is described in more detail below.
Alternatively, other lenses are possible that allow different
magnifications. Single and compound lenses that are designed to be
achromats over the desired infrared spectral region can also be
used.
[0064] Further, as shown in the embodiment illustrated in FIG. 1A,
the transmitted rays 20T or the reflected rays 22R that are
collected by the first lens 32 are directed at the
transmitter-redirector 30 that is positioned between the first lens
32 and the second lens 34 in this example. In this embodiment, if
the transmitter-redirector 30 is a fifty percent (50%) beam
splitter, the transmitted rays 20T or the reflected rays 22R that
are collected by the first lens 32 are split into (i) the imaged
rays 18A that are imaged on the image sensor 18, and (ii) discarded
rays that are directed away from the image sensor 18.
[0065] The image sensor 18 senses the imaged rays 18A and converts
the imaged rays 18A (the optical image) into an array of electronic
signals that represents an image of the sample.
[0066] In certain embodiments, the image sensor 18 includes a two
dimensional array of photosensitive elements (pixels) (e.g. a focal
plane array (FPA)) that are sensitive to the wavelength of the
illumination beams 20l, 22l that are used to construct a
two-dimensional image. The spacing between the pixel elements is
referred to as the pitch of the array. For example, if the
illumination beams 20l, 22l are in the MIR range, the image sensor
18 is a MIR imager. More specifically, if the illumination beams
20l, 22l are in the infrared spectral region from two to twenty
.mu.m, the image sensor 18 is sensitive to the infrared spectral
region from two to twenty .mu.m.
[0067] Examples of suitable infrared image sensors 18 include (i)
vanadium oxide (VO.sub.x) microbolometer arrays such as the FPA in
the FLIR Tau 640 infrared camera that are typically responsive in
the seven to fourteen .mu.m spectral range; (ii) mercury cadmium
telluride (HgCdTe or MCT) arrays such as those in the FLIR Orion
SC7000 Series cameras that are responsive in the 7.7 to 11.5 .mu.m
spectral range; (iii) indium antimonide (InSb) arrays such as those
in the FLIR Orion SC7000 Series cameras that are responsive in the
1.5 to 5.5 .mu.m spectral range; (iv) indium gallium arsenide
(InGaAs); (v) uncooled hybrid arrays involving VOx and other
materials from DRS that are responsive in the two to twenty .mu.m
spectral range; or (vi) any other type of image sensor 18 that is
designed to be sensitive to infrared light in the two to twenty
.mu.m range and has electronics allowing reading out of each
element's signal level to generate a two-dimensional array of image
information.
[0068] In alternative, non-exclusive embodiments, the pixel
dimensions for the image sensor 18 can be five, eight, ten, twelve,
thirteen, seventeen, twenty-five, thirty-five, and fifty .mu.m per
side, for example. Additionally, the pixels can be square,
rectangular, or any other shape. As non-exclusive examples, the
image sensor 18 can be designed to include a 50.times.50 array of
pixels; a 100.times.100 array of pixels, a 200.times.200 array of
pixels, a 320.times.240 array of pixels, a 400.times.400 array of
pixels, a 500.times.500 array of pixels, a 640.times.480 array of
pixels, or another sized array of pixels. Further, the arrays can
be square or rectangular, or masked for a specific shape, either
physically or through data processing.
[0069] In one non-exclusive example, the image sensor 18 can be a
microbolometer array having a pixel pitch of 17 .mu.m and a frame
size of 640.times.512, resulting in a physical FPA size of 10.88
mm.times.8.7 mm. With five times magnification for the first lens
32, i.e. the objective lens, and the second lens 34, i.e. the
projection lens, this results in an area imaged at the sample 10 of
2.2 mm.times.1.7 mm. Therefore, the size of the illumination beam
20, 22 should be sufficient to provide illumination across this
area on the sample 10. If the 95% beam diameter is at least three
millimeters, the illumination beam 20, 22 can provide appropriate
illumination across the sample 10 as necessary.
[0070] In certain embodiments, the present invention allows the use
of lower priced, room temperature image sensors 18, e.g., FPAs such
as microbolometers. These FPAs require lower power consumption and
have smaller overall volume, such that field-deployable and
commercial instruments become more practical. Additionally, the use
of tunable infrared lasers, such as QC lasers 14A, 14B, generates
enough light to allow the use of these less-sensitive room
temperature FPAs. In particular, the use of such an FPA allows for
a complete image to be captured at each wavelength. Moreover, due
to the higher power provided by such lasers 14A, 14B, less signal
averaging is thus required, meaning that it is possible to rapidly
tune the laser 14A, 14B and then build up a spectral image cube for
analysis in tens of seconds, rather than the minutes generally
required for FTIR microscopes.
[0071] As a non-exclusive example, tunable infrared lasers, such as
QC lasers 14A, 14B, can generate between approximately 0.2 mW to 20
mW at a single wavelength. This will provide enough intensity to
overcome the background pixel noise level of less-sensitive
microbolometer arrays.
[0072] As provided herein, in certain embodiments, the imaging
device 12 is designed so that (i) the illumination rays 20l
generated by the first laser source 14A are directed at the sample
10 without splitting and recombining the illumination rays 20l,
e.g. illumination rays 20l follow a single path to the sample 10;
(ii) the illumination rays 22l generated by the second laser source
14B are directed at the sample 10 without splitting and recombining
the illumination rays 22l, e.g. the illumination rays 22l follow a
single path to the sample 10; and (iii) the imaged rays 18A travel
from the sample 10 to the image sensor 18 without splitting and
recombining the imaged rays 18A, e.g. the imaged rays 18A follow a
predominantly single path to the image sensor 18. With this design,
potential drawbacks from the use of a temporally coherent light
source, such as certain interference effects, e.g., interference
fringes, can be avoided. Spatial coherence occurs when the
variation in the electric field wavefront of the light is similar
across an illuminated area. The effects on imaging of spatial
coherence include speckle and diffraction. Temporal coherence means
that the electric field of the light exhibits the same oscillation
pattern over a significant period of time, such as a sinusoidal
oscillation. Whereas spatial coherence can occur even for waves
that do not have a regular, sinusoidal electric field, temporal
coherence requires a periodic, regular oscillation in the electric
field. This presents a particular challenge for imaging because
laser light originating from a single source, which is subsequently
split such that portions of the laser light travel different paths,
and which is then recombined, can exhibit interference effects. For
example, the effects of temporal coherence can be seen in terms of
interference fringes. More particularly, light emanating from an
illuminating laser that is split and allowed to travel two separate
paths before being rejoined at a sample, can result in interference
fringes being evident on an illuminated sample. As detailed herein,
the present design effectively enables such potential drawbacks to
be avoided.
[0073] Additionally, as illustrated in FIG. 1A, the imaging
microscope 12 can further include and/or be coupled to a processing
device 36 that includes one or more processors and/or storage
devices. For example, the processing device 36 can receive
information from the pixels of the image sensor 18 and generate the
image of the sample. Further, the processing device 36 can control
the operation of the laser sources 14A, 14B and the stage assembly
15.
[0074] FIG. 2 is a simplified schematic illustration of the sample
10 and another embodiment of an imaging microscope 212 having
features of the present invention. The imaging microscope 212
illustrated in FIG. 2 is somewhat similar to the imaging microscope
12 illustrated and described above in relation to FIG. 1A. For
example, the imaging microscope 212 includes a temporally coherent
beam source 214 that includes a laser source 214A, a stage assembly
215, an imaging lens assembly 216, an image sensor 218, and a
processing device 236 that are somewhat similar to the
corresponding components illustrated and described above in
relation to FIG. 1A. However, in the embodiment illustrated in FIG.
2, the imaging microscope 212 is designed to only function in the
transmission mode with an in line format, and the imaging
microscope 212 does not function in the reflection mode.
[0075] In this embodiment, because the imaging microscope 212 is
only designed to function in transmission mode, the imaging
microscope 212 can be designed without the illumination optics that
are included in the embodiment illustrated in FIG. 1A to enable the
imaging microscope 12 to alternatively function in reflection mode.
Accordingly, in this embodiment, the imaging microscope 212 does
not include the reflection illumination lens assembly 26, the
redirector 28 and the transmitter-redirector 30 that are at least
optionally included in the embodiment illustrated in FIG. 1A.
[0076] Similar to the previous embodiment, the temporally coherent
beam source 214 emits a temporally coherent illumination beam 220
that includes a plurality of illumination rays 220l for
illuminating and analyzing the sample 10 in transmission mode.
[0077] The transmission illumination lens assembly 224 can again
adjust the illumination beam 220 so that the illumination beam 220
illuminates a two dimensional transmission illuminated area, e.g.,
the transmission illuminated area 10A illustrated in FIG. 1B, on
the sample 10 all at once.
[0078] Subsequently, at least some of the transmitted rays 220T
that are transmitted through the sample 10 are then directed toward
the image sensor 218 with the imaging lens assembly 216. The
transmitted rays 220T collected by the imaging lens assembly 216
and directed at the image sensor 218 are referred to as imaged rays
218A. As with the previous embodiment, the imaging lens assembly
216 can include a first lens 232 and a second lens 234 that
cooperate to form an image of the sample 10 on the image sensor
218. Alternatively, the imaging lens assembly 216 can include
greater than two lenses or only one lens.
[0079] FIG. 3 is a simplified schematic illustration of the sample
10 and still another embodiment of an imaging microscope 312 having
features of the present invention. The imaging microscope 312
illustrated in FIG. 3 is somewhat similar to the imaging microscope
12 illustrated and described above in relation to FIG. 1A. For
example, the imaging microscope 312 includes a temporally coherent
beam source 314 with a laser source 314B, a stage assembly 315, an
imaging lens assembly 316, an image sensor 318, and a processing
device 336 that are somewhat similar to corresponding components
illustrated and described above in relation to FIG. 1A. However, in
the embodiment illustrated in FIG. 3, the imaging microscope 312 is
designed to only function in the reflection mode, and the imaging
microscope 312 does not function in the transmission mode. More
particularly, because the imaging microscope 312 is only designed
to function in reflection mode, the imaging microscope 312 can be
designed without the transmission illumination lens assembly 24
that is at least optionally included in the embodiment illustrated
in FIG. 1A.
[0080] Similar to the previous embodiment, the temporally coherent
beam source 314 emits a temporally coherent illumination beam 322
that includes a plurality of illumination rays 322l for
illuminating and analyzing the sample 10 in reflection mode.
[0081] The reflection illumination lens assembly 326 can again
adjust the illumination beam 322 so that the illumination beam 322
illuminates a two dimensional reflection illuminated area, e.g.,
the reflection illuminated area 10C illustrated in FIG. 1C, on the
sample 10 all at once.
[0082] Subsequently, at least some of the reflected rays 322R that
are reflected from the sample 10 are then directed toward the image
sensor 318 with the imaging lens assembly 316. The reflected rays
322R collected by the imaging lens assembly 316 and directed at the
image sensor 318 are referred to as imaged rays 318A. As with the
previous embodiment, the imaging lens assembly 316 can include a
first lens 332 and a second lens 334 that cooperate to form an
image of the sample 10 on the image sensor 318. Alternatively, the
imaging lens assembly 316 can include greater than two lenses or
only one lens.
[0083] In this embodiment, the reflection illumination lens
assembly 326 again includes one or more lenses 326A (two are
illustrated in FIG. 3), a redirector 328, and a
transmitter-redirector 330 that are similar to the corresponding
components described above and illustrated in FIG. 1A.
[0084] FIG. 4 is a simplified flowchart demonstrating the use of an
imaging microscope having features of the present invention to
analyze a sample. Although it is disclosed that the steps employed
in the use of the imaging microscope are performed in a certain
order, it should be noted that the steps can be performed in a
different order, and/or one or more of the steps can be combined or
eliminated without altering the overall intended scope and breadth
of the present invention.
[0085] Initially, in step 401, a sample is obtained that it is
desired to analyze utilizing the imaging microscope. Additionally,
in step 403, the sample is visually inspected to determine whether
the sample is appropriate for analysis in transmission mode or
reflection mode. In particular, if the sample is thin and/or
substantially transparent, then the sample is more appropriate for
analysis in the transmission mode. Alternatively, if the sample is
substantially opaque such that the illumination beam will likely be
reflected by the sample, then the sample is more appropriate for
analysis in the reflection mode.
[0086] In step 405, the sample is positioned near a temporally
coherent beam source within the imaging microscope for analysis.
Further, in step 407, the temporally coherent beam source of the
imaging microscope, e.g., a laser source that operates in the
infrared spectral region between two and twenty .mu.m, is tuned to
a particular wavelength.
[0087] Then, in step 409, the beam source is activated in order to
generate a first image of the sample. As disclosed herein above,
the beam source illuminates a two-dimensional area of the sample
all at once, which is then imaged onto an image sensor, e.g., an
image sensor that is responsive somewhere in the infrared spectral
region from two to twenty .mu.m, through one or more lenses, e.g.,
an objective lens and a projection lens. The illumination provided
by the beam source is necessarily controlled so that a set of
single path rays from the illumination beam traverses a single path
before impinging on the sample and between the sample and the image
sensor. Stated another way, the illumination provided by the beam
source is controlled so that the set of single path rays are not
split and recombined between the beam source and the sample, and
the set of single path rays are not split and recombined between
the sample and the image sensor.
[0088] If it has been determined that the imaging microscope should
be appropriately utilized in transmission mode for the particular
sample being analyzed, then the beam source should be activated so
as to substantially directly illuminate the sample. Alternatively,
if it has been determined that the imaging microscope should be
appropriately utilized in reflection mode for the particular sample
being analyzed, then the beam source should be activated so as to
illuminate the back side of the sample utilizing the appropriate
optical elements. It should be noted that if an insufficient image
is generated with the imaging microscope in the mode chosen, i.e.
either transmission mode or reflection mode, then the alternative
mode can be activated to provide a more sufficient and/or
appropriate image generated from the sample.
[0089] In step 411, the beam source is deactivated, i.e. is turned
off, and a second image of the sample is captured by the image
sensor without the use of the temporally coherent beam source.
Then, in step 413, the second image of the sample acquired without
the beam source is subtracted from the first image of the sample
acquired utilizing the beam source to create a differential image
of the sample that consists entirely of transmitted or reflected
light from the beam source.
[0090] Subsequently, in step 415, the process of steps 407 through
413 is repeated as necessary with the beam source tuned to
additional appropriate wavelengths. This creates a set of images at
different wavelengths of the beam source, known as a spectral image
cube, or hypercube. Then, in step 417, the spectral image cube can
be analyzed at each pixel or set of pixels to generate a
transmission or reflection spectrum. Next, in step 419, the
spectrum can then be analyzed to determine properties of the sample
at different positions across the sample. These properties can be
chemical, structural, or phase, for example. Finally, in step 421,
the analyzed data is then used to create a two-dimensional map of
sample properties that can be visually overlaid on a picture of the
sample to identify regions of the sample with different sample
properties.
[0091] In summary, as disclosed herein, the present invention
allows the creation of an infrared imaging microscope for spectral
analysis that has many advantages over traditional technology based
on FTIR spectrometers. In particular, the present invention is
meant to deal with the difficulties of illumination and imaging
with a temporally coherent illumination beam that originates from a
temporally coherent beam source such as a laser. As disclosed
herein, the way to provide uniform, interference fringe free
illumination is to eliminate multiple beam paths from the beam
source to the sample 10, and from the sample 10 to the image
sensor. More specifically, as provided herein, the optics are
designed to allow interference-free illumination of a sample by
using a illumination beam that has been transformed through
reflections and lens elements alone, and not split into different
paths and recombined. Similarly, the optics train for imaging the
sample 10 onto the image sensor, e.g., onto a focal plane array, is
meant to interact with the largely single transmission or
reflection beam path from the laser illumination, and to map this
to the image sensor without splitting into different paths and
recombining.
[0092] In one embodiment, the imaging microscope can include a
illumination beam, e.g., an infrared laser beam from a tunable QC
laser, which can be directly pointed to the sample 10 in
transmission mode. In such embodiment, the illumination beam, e.g.,
an infrared laser beam, can have an extent of approximately 3
mm.times.3 mm, so it illuminates the sample 10 nearly uniformly,
without visible interference fringes. This direct illumination
removes multiple beam paths. Without this invention, illumination
with such an illumination beam would produce significant
interference effects due to the temporal coherence of the beam
source. With the invention, these effects are gone, allowing fast
acquisition of an image with no interference artifacts.
[0093] Additionally, in reflection mode, the illumination beam can
be coupled in through a transmitter-redirector, e.g., a beam
splitter, to provide the same effect. Because the illumination beam
traverses an objective lens before impinging on the sample 10, an
illumination lens can be employed to project the illumination beam
onto the sample 10 with sufficient extent to provide sufficient
illumination.
[0094] Moreover, the present invention allows the use of a compact
optical train based on refractive optical components. This in turn
lends itself to a compact instrument design that is easier to
manufacture, more robust for field deployment, and more cost
effective for commercial products.
[0095] While a number of exemplary aspects and embodiments of an
imaging microscope 12 have been discussed above, those of skill in
the art will recognize certain modifications, permutations,
additions and sub-combinations thereof. It is therefore intended
that the following appended claims and claims hereafter introduced
are interpreted to include all such modifications, permutations,
additions and sub-combinations as are within their true spirit and
scope.
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